From toukie: at :zui.unizh.ch  Thu Sep  4 12:28:48 1997
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Date: Thu, 04 Sep 1997 18:12:43 +0200
To: chemistry-: at :-www.ccl.net
From: "Hr. Dr. S. Shapiro" <toukie- at -zui.unizh.ch>
Subject: MOPAC question
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Dear Colleagues;

	I would like to do a MNDO optimisation for the molecule 
p-tolylacetylene; however, when I run MOPAC 6.0 using the Z-matrix
for this molecule with the keywords "nointer ef precise polar", the
calculation aborts because MOPAC rejects structures that appear to 
have too many atoms all in a straight line [e.g., the C(ar)-C#C-H atoms are
aligned at 180 degrees].  I understand that MOPAC _is_ able to run this
calculation if Cartesian coordinates are substituted for the MOPAC Z-matrix
in the input.  However, I can't find any useful information about this
option in the MOPAC 6.0 manual (though I confess that I _may_ have
overlooked this information whilst going through my hard copy of the user's
manual).

	Therefore, I'd be grateful to anyone who can give me detailed advice about
how to run a MOPAC calculation for p-tolylacetylene, with or without
Cartesiabn coordinates as the input.  If Cartesian coordinates _must_ be
used as the input, what special keywords do I need, and exactly how (for
example) should this Cartesian coordinate input be written?

	Thanks in advance to all responders.

Sincerely,

S. Shapiro
toukie ":at:" zui.unizh.ch